We have witnessed a lot of death of COVID-19 patients in the second wave of the COVID-19 pandemic and majority of the deaths has been attributed to the low oxygen levels in COVID patients.

After a number of theories and counter theories, finally, there seems to be an explanation as to why there are low oxygen levels in COVID patients, according to the latest study published in the journal Stem Cell Reports.

It may be mentioned here that SARS-CoV-2, which causes COVID-19, infects immature red blood cells (RBC), reducing oxygen in the blood and impairing the immune response, say researchers.

The latest study sheds light on why many COVID-19 patients, even those not in the hospital, are suffering from hypoxia - a potentially dangerous condition in which there is decreased oxygenation in the body's tissues.

The study also shows why the anti-inflammatory drug dexamethasone has been an effective treatment for those with the virus.

Shokrollah Elahi, Associate Professor in the Faculty of Medicine and Dentistry at the University of Alberta, Canada, said that low oxygen levels in COVID patients have been a major problem of most of the patients suffering from the disease.

"Because of that, we thought one potential mechanism might be that Covid-19 impacts red blood cell production," Elahi added.

It's worth mentioning here that Elahi's team was the first in the world to demonstrate that immature RBCs expressed the receptor ACE2 and a co-receptor, TMPRSS2, which allowed SARS-CoV-2 to infect them.

The team examined the blood of 128 COVID-19 patients, which included patients from various stages from critically ill and admitted to the ICU, to those who had moderate symptoms and were admitted to hospital.

The study subjects also included patients who had a mild version of the disease and only spent a few hours in the hospital.

The research team found that as the disease became more severe, more immature RBCs flooded into blood circulation, sometimes making up as much as 60 per cent of the total cells in the blood.

"By comparison, immature RBCs make up less than one per cent, or none at all, in a healthy individual's blood," reported news agency IANS quoting the study.

The team also found the dexamethasone drug suppresses the response of the ACE2 and TMPRSS2 receptors to SARS-CoV-2 in immature RBCs, reducing the opportunities for infection.

The drug also increases the rate at which the immature RBCs mature, helping the cells shed their nuclei faster.

"Without the nuclei, the virus has nowhere to replicate," the researchers said.